Die Glocke: The Legend of the Nazi Bell

Like most other militaries of the time, the Nazi army conducted extensive classified research into all aspects of warfare, from rocketry to drugs, tank improvements and so on. They also delved into more exotic realms, and their endeavors remain a subject of enduring fascination in the modern age. Perhaps the most famous of these legendary experiments is something known as Die Glocke, or the Nazi Bell. But what is it supposed to be, exactly? What does it do? And, if it is real, where did it end up?